Longer Range Wired Protocols

To minimize cost they want to use just two wires, either a coaxial cable, a twisted pair or a shielded twisted pair. They want an asymmetric standard; high bandwidth video goes in one direction, low bandwidth control signals go in the other direction, sometimes control goes in both directions. They also want the option to send power over the same two wire cable. One problem is that high frequency signals attenuate very rapidly. Doing all of this on a single pair of wires is a miracle of mixed signal engineering [16]. Here are the available solutions to this problem.

Serializer/Deserializer (SerDes)  converts between parallel and serial data. SerDes uses differential pairs.  On FPGAs, SerDes typically operates from 1,25 to 5 GHz. Serdes may be exposed on the external pins, or it may be used as part of a more complex protocol such as USB or MIPI. GateMate and the Lattice NX33 are low cost FPGAs with exposed SerDes.

Gigabit Multimedia Serial Link (GMSL) is a SerDes version by Maxim Corporation, Their products allow the I2C control to be on a separate side channel from the high bandwidth video.

ASA MotionLink is a SerDes version which was created  by the Automobile Serdes Alliance (ASA) , an industry group whose goal is to “provide standards for asymmetric high speed P2P communication in vehicles.”

MIPI C-Phy was created by the MIPI alliance for automotive and other applications which need longer distance communication.

MIPI A-Phy is a merger between the proprietary MIPI C-Phy and the more open ASA MotionLink.  Many vendors hope that this will be the winner for longer cable lengths. But like all things created by large committees with compromises, it is a bit complex.